From the Rolls-Royce experimental archive: a quarter of a million communications from Rolls-Royce, 1906 to 1960's. Documents from the Sir Henry Royce Memorial Foundation (SHRMF).
Calculations for armature design, conductor count, and back E.M.F. of an electric motor.
| Identifier | ExFiles\Box 64\2\ scan0073 | |
| Date | 1st June 1927 guessed | |
| -2- Contd. Assume a useful polar flux density of 6750 lines per cm² reckoned on the minimum pole face. Armature diameter 3.100" Armature circumference corresponding to 69% polar embrace = (69/400) x π x 3.100 = 1.68" = 4.27 cm. Armature length = 2.750" = 6.99 cm. Useful flux per pole = 6750 x 4.27 x 6.99 = 201,000. Number of conductors = (Tb x 10⁸) / (1.41 P Ø C) = (110 x 2 x 10⁸) / (1.41 x 4 x 201,000 x 166.) = 117, say 116. This necessitates two turns per coil, 29 coils and slots. Motor speed = 455 R.P.M. Back E.M.F. when rolling engine = (Ø Z N P) / (60 x 10⁸ x b) = (201,000 x 116 x 455 x 4) / (60 x 10⁸ x 2) = 3.54 volts. Contd. | ||